The invention relates to pyrotechnic caps and particularly to hermetically-sealed pyrotechnic caps capable of being activated by radiant energy in the form of light and/or heat.
In the aforementioned U.S. Pat. No. 4,130,082, there is described a unique concept in the production of high intensity audible and visual signals. As described therein, it has been discovered that hermetically-sealed plastic caps having certain pyrotechnic compositions therein can be instantaneously activated by the highly intense light and/or heat from an adjacent chemical flashlamp to produce an aubible signal also of high itensity (e.g. approaching 165 decibels). The preferred activating flashlamps are percussively-activated chemical flashlamps as presently utilized in the photoflash products manufactured and sold by the assignee of the instant invention under the name MAGICUBE. By chemical flashlamp is meant one having a glass envelope containing a combustion-supporting atmosphere and a quantity of filamentary combustible material (e.g. shredded zirconium) therein. Percussive activation of such a lamp occurs when a metal tube which comprises part of the lamp is deformed by mechanical impact whereupon primer material therein deflagrates up through the tube to ignite the filamentary combustible material in the lamp's envelope. As also described in U.S. Pat. No. 4,130,082, it is possible to activate the sealed caps using other varieties of chemical flashlamps such as those which are electrically activated. One example of this latter type are flashlamps currently utilized in the photoflash products manufactured and sold by the assignee of the instant invention under the name FLIP-FLASH.
A primary use for the device in U.S. Pat. No. 4,130,082 is as an intrusion alarm. The device may also comprise part of an alarm system wherein a suitable detector is used to receive the device's output and thereafter perform an auxillary function (e.g. emit a prolonged, high intensity signal). Quite understandably, devices such as alarm systems must possess a high degree of reliability. Accordingly, it is essential that the cap member which comprises an integral part of the device must possess a similar functioning ability.
It has been determined that the presence of moisture within the cap, even in relatively minor quantities, can adversely affect both the cap's reliability and the uniformity of loudness of the emitted audible signal. This moisture may enter the cap either during manufacture thereof or subsequent to said manufacture by penetration of a defective seal. Under extreme conditions (e.g. high relative humidity for prolonged periods at elevated temperatures), it might also be possible for moisture to permeate the preferred plastic materials used for the cap's container.
It is believed, therefore, that a pyrotechnic cap member including means for visibly indicating the presence of harmful quantities of moisture therein in order that the cap user can effect replacement of the member would constitute a significant advancement in the art.